The overall objective is to improve the safety and health of firefighters and rescue workers who use a self-contained breathing apparatus (SCBA) in hazardous environments. The specific aim is to develop an electromechanical pressure regulator that assures positive pressure in the SCBA facepiece even during strenuous activity. Positive pressure is essential to protect health and safety, because the facepiece pressure keeps out potentially poisonous gases from the environment. The proposed electromechanical pressure regulator overcomes the drawbacks of conventional, mechanical regulators. The key innovation is the combination of advanced micromachined pressure sensors located in the facemask, lightweight electromechanical valves, and an innovative electronic control system. In the electromechanical regulator, very small pressure sensors will be located directly at the critical sealing surfaces of the facemask. Rapid response and a wide control range of an electromechanical valve prevent overbreathing. The electronic control unit can warn the user of falling pressure in the mask, which can result from an ineffective facemask seal. Phase I will prove feasibility by fabricating a proof-of- concept regulator and testing it under extreme conditions using a SCBA facemask and a breathing machine. Phase II will develop and demonstrate prototype regulators for commercial SCBAs which meet all relevant NIOSH and NFPA standards. PROPOSED COMMERCIAL APPLICATION: The primary commercial application of the proposed electromechanical regulator is for a pressure-demand, positive-pressure self-contained breathing apparatus worn by firefighters and hazardous materials workers. The device can be incorporated in new SCBA units and can also be retrofit to units already in the field. We estimate the potential market to be in the range of 10,000 to 100,000 per year. Creare has teamed with one of the largest manufacturers of SCBAs to commercialize the electromechanical SCBA regulator.